Bash - checking variable value

Question

I am trying to check if the the variable $userSelection is not having value 1, 2 or 3, then I display error message. Tried the following and other combinations, but no luck.

if [ $userSelection -ne 1 || $userSelection -ne 2 ] || [ $userSelection -ne 2 || $userSelection -ne 3 ]
then 
    echo "Option selected not valid...please try again."
fi

Am getting error [: missing]'`.

You've got a rogue bracket in there [ $userSelection -ne 2 Easy to miss with all those bars. — JNevill
– JNevill, Commented Mar 1, 2018 at 18:51
[ is a command. It has the odd behavior of requiring that its last argument be ]. You are trying to run the command [ $userSelection -ne 1 and then (if it is successful) the command $userSelection -ne 2. You must stop thinking of [ as being a symbol in the grammar of the shell. It is just a command. This is often more clear if you spell it test (which is exactly the same as [, except that it does not require that its final argument be ]) — William Pursell
– William Pursell, Commented Mar 1, 2018 at 19:08
@JNevill Thanks for highlighting that...classic mistake of overlooking — ksa_coder
– ksa_coder, Commented Mar 1, 2018 at 19:23
@JNevill Actually, that [ is necessary to start a new command, because [ doesn't support ||. He's actually missing quite a few brackets. — chepner
– chepner, Commented Mar 1, 2018 at 19:36

chepner · Accepted Answer · 2018-03-01 19:33:54Z

4

For your actual needs the right code should be the following:

if [ "$userSelection" -ne 1 ] && [ "$userSelection" -ne 2 ] && [ "$userSelection" -ne 3 ]
then 
    echo "Option selected not valid...please try again."
fi

From what you are saying the only right choices should be 1,2 or 3.

edited Mar 1, 2018 at 19:33

chepner

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answered Mar 1, 2018 at 19:04

shadowsheep

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1 Comment

ksa_coder Over a year ago

Yes! Thanks a bunch

chepner · Accepted Answer · 2018-03-01 19:45:50Z

1

Missing brackets aside, the simplest way to make such a check is with a case statement instead:

case $userSelection in
   1|2|3) ;;
   *) echo "Option selected not valid...please try again." ;;
esac

edited Mar 1, 2018 at 19:45

answered Mar 1, 2018 at 19:35

chepner

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